1. Field of the Invention
The present invention relates generally to electrical protection devices, and particularly to electrical protection devices with safety features.
2. Technical Background
As those of ordinary skill in the art understand, an electric circuit comprises many different electrical wiring devices disposed at various locations throughout a structure. These devices include outlet receptacles, which may be combined with other wiring devices such as switches, lighting devices and protective wiring devices. Ground fault circuit interrupters (GFCIs), and arc fault circuit interrupters (AFCIs) are examples of protective devices in electric circuits. Each of the aforementioned protective devices have interrupting contacts for breaking the connection between the line terminals and load terminals when the protective device detects a fault condition. The connection is broken to interrupt the load current and thereby remove the fault condition. Fault conditions include those that result in risk electrocution of personnel, or fire. The outlet receptacles are disposed in duplex receptacles, raceway, multiple outlet strips, power taps, extension cords, light fixtures, appliances, and the like. Duplex receptacles may be configured for installation in outlet boxes. Once installed, a faceplate may be attached to the cover of the outlet receptacle or to the junction box to complete the installation.
Most of these devices have line terminals for connection to the power line, and load terminals for connection to a load. The load terminals include receptacle contacts and feed-thru terminals. The receptacle contacts are configured to accommodate the blades of a plug connector, which are inserted to provide power to a load. Feed-thru terminals, on the other hand, are configured to accommodate wires which are connected to one or more additional receptacles, known as a downstream receptacles. The downstream receptacle may include a string of downstream receptacles that comprise a branch circuit of an electrical distribution system.
One safety issue that heretofore has not been adequately addressed relates to the insertion of foreign objects into receptacle openings. In many cases, young children and toddlers insert objects such as paper clips or screwdriver blades into the receptacle contact openings. Unfortunately, this scenario often results in an electric shock, burns, or electrocution.
In one approach that has been considered, the electrical receptacles in the wiring device are equipped with shuttered openings that prevent the insertion of foreign objects into the receptacle contact openings. One drawback to this approach relates to the ineffectiveness of related art designs. If objects are placed into both openings, the shutter will typically operate, exposing the child to a shock hazard. What is needed is a shutter mechanism that only opens when an actual plug is being inserted into the receptacle.
Another drawback to this approach relates to the complexity of related art shutters. Many shutter designs comprise multiple parts and spring elements that are not integrated into a unitary sub-assembly. The cost and time of assembling the shutter mechanism and the space taken up by their multiple parts limit the usage of these designs. Further, automated environments often generate vibrations and mechanical forces that tend to introduce failure modes. What is needed is a unitary protective shutter assembly suitable for use within automated manufacturing processes.